1. Field of the Invention
The present invention relates to an inverter power generator that generates AC power with a synchronous motor driven by a prime mover such as an engine, converts the AC power into DC power, and inverts the DC power with an inverter into AC power of a required frequency.
2. Description of Related Art
The inverter power generator is widely used to generate electric power with the use of a prime mover such as an engine. The inverter power generator connects an output shaft of the engine to a rotary shaft of a synchronous motor, drives the synchronous motor with the engine to generate AC power, converts the AC power with a converter into DC power, and inverts the DC power with an inverter into AC output power of required voltage and frequency. The AC output power is supplied to a load such as a motor, a lamp, or the like that is connected to the inverter.
If the load connected to the inverter of the inverter power generator is a motor (hereinafter referred to as “load motor”) such as an induction motor, there is a possibility that the load motor causes a rush current at startup to cause an excessive current to semiconductor elements arranged in a control unit of the inverter. If the excessive current is larger than a maximum rated current of the semiconductor elements, the semiconductor elements will malfunction to break the control unit.
To prevent this problem, Japanese Unexamined Patent Application Publication No. 2003-111428 (Patent Document 1) discloses a technique of dropping an output voltage of the inverter according to the magnitude of an output current of the inverter, thereby suppressing a load current and a current passed to the control unit.